1. Field of the Invention
The invention relates to a backing web for many uses, but particularly for resilient flooring materials which are applied and adhered to floors or other like surfaces. Many products of resilient flooring materials have a backing sheet web of a fibrous, felted, matted, non-woven, or other construction comprising a major proportion of cellulosic fiber, such as wood pulp, rags, cotton linters, rayon, or the like. Such backing webs impart many useful properties to the resilient flooring material, such as an increase of strength, wear life, and servicability, as well as characteristics of the resilient flooring material. The backing web, depending upon the type and composition of backing web, can give the product various other desirable properties, such as high resiliency, good feel, and high resistance to abrasion, as well as adherence to a wall or floor surface by use of a suitable mastic.
When resilient flooring materials are installed on floor surfaces of considerable width or length, particularly as is commonly encountered in mobile homes, offices, public buildings, schools, nautical construction, and the like, a problem has been observed immediately after installation of a resilient flooring material with a back web, particularly when installed in relatively great lengths, such as 100 feet or more. Manifesting itself in a tendency of the resilient flooring material to grow in length, or shrink, the problem appears in the form of swelling, buckling, formation of upraised regions, ridges or other undesirable manifestations which can detract considerably from the appearance of the floor covering. Furthermore, this undesirable tendency to growth appears to depend upon the level of relative humidity at the time of installation of the resilient flooring material, being greater at relatively low percentages of relative humidity, a condition under which many installations of floor coverings frequently are carried out.
In response to problems associated with an undesirable growth tendency in resilient flooring material having a backing web, certain approaches have been made. For instance, asbestos has been used to overcome such growth tendency and to impart dimensional stability to the resilient flooring material product when a major proportion of asbestos fibers are incorporated within the material making up the backing web of a resilient flooring material. However, human health hazards associated with industrial use of asbestos have come to light in recent years as defined in permissible exposure standards published in the U.S. Federal Register, Vol. 39, No. 125, Part II, pp. 23543-45, June 27, 1974, under provisions of the Occupational Safety and Health Act. These health hazards, including the possibility of serious diseases of the human lungs have led to a widespread search for suitable substitutes for asbestos in all industrial and consumer products containing greater than insignificant amounts of asbestos.
Further problems are encountered from curling of a resilient flooring material having a backing web when the product is removed from a region of lower humidity to an environment of higher humidity. The unbacked layers of flooring material exhibit little or no lateral extension under such conditions, but an associated cellulosic backing web tends to extend laterally when the surrounding environment changes in relative humidity to more humid conditions. Such differential extension causes upward curling at the edge of a resilient flooring material applied with the backing web downward against a subflooring material.
Only by providing a backing web with substantial dimensional stability can the dual problems of growth and curling in a resilient flooring material be avoided.
When used alone the backing web can be manufactured into map paper, chart paper, graph paper, or other papers with desirable properties, such as flexibility, dimensional stability and absence of problems identified above as associated with use of asbestos.
When used alone the backing web can form other useful asbestos-free products with dimensional stability and desirable properties, such as gasketing, filters, acoustical board and packaging. Other products with certain of these advantages can be made from the backing web alone, inclluding visor board, shoe insoles and hat brim material.
2. Description of the Prior Art
Methods are known for reducing the growth of cellulose-backed flooring products, such as the method disclosed in U.S. Pat. No. 4,066,183 to Winters, et al. This patent discloses including a growth inhibitor in the cellulosic backing of the flooring product, the growth inhibitor being a soluble salt containing aluminum or other trivalent metal cation. The present invention teaches away from addition of a growth inhibitor such as that described in the Winters et al patent by focusing instead on the nature and composition of fiber used.
Also known are methods for papermaking, including wet end addition of neoprene latex added to a fiber slurry prior to sheet formation, where cellulose, asbestos, glass synthetic fibers, and the like, can comprise the slurry, as well as wet web and dry web impregnation of fibrous mats, as disclosed in technical product literature published by the Elastomer Chemicals Department, E. I. DuPont de Nemours, Inc., Wilmington, Delaware, entitled "Neoprene Treated Paper" by C. H. Gelbert.
The incorporation of rubber binder in fibrous webs containing cellulose fiber, asbestos fiber, and pigments by dry web impregnation and latex deposition methods has also been described in technical product literature published by the B. F. Goodrich Chemical Company, Cleveland, Ohio, entitled "Latex Manual HL-2".
Use of glass fibers in papermaking is known, where fine glass fiber is introduced into a dispersion which can be blended with wood pulp. See, for example, in the article by C. W. Charon & L. C. Renaud, Pulp and Paper, October 1971, pp. 84-88, the use of glass fibers in pulp to increase dimensional stability of paper, such as papers for application in blueprints, drafting papers, charts or maps. Such papers, however, have poor edge tearing resistance, poor resistance to folding and poor wetting resistance.
Other patents illustrating related concepts in the prior art are the following:
U.S. Pat. No. 2,165,788--July 11, 1939--Elmendorf PA1 U.S. Pat. No. 3,293,094--Dec. 20, 1966--Nairn et al PA1 U.S. Pat. No. 3,293,108--Dec. 20, 1966--Nairn et al